261865410 has 64 divisors (see below), whose sum is σ = 663707520. Its totient is φ = 65940480.

The previous prime is 261865397. The next prime is 261865453. The reversal of 261865410 is 14568162.

It is a Curzon number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 246280 + ... + 247340.

It is an arithmetic number, because the mean of its divisors is an integer number (10370430).

Almost surely, 2^261865410 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 261865410, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (331853760).

261865410 is an abundant number, since it is smaller than the sum of its proper divisors (401842110).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

261865410 is a wasteful number, since it uses less digits than its factorization.

261865410 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1523.

The product of its (nonzero) digits is 11520, while the sum is 33.

The square root of 261865410 is about 16182.2560231879. The cubic root of 261865410 is about 639.7732025166.

The spelling of 261865410 in words is "two hundred sixty-one million, eight hundred sixty-five thousand, four hundred ten".